Investigation on Deformation Behavior in the Surface of Metal foil with Ultrasonic Vibration-Assisted Micro-Forging

Excitation of the acoustic field leading to the Blaha effect affects the plasticity of the material significantly in ultrasonic vibration-assisted forming. In a micro-forming field, the effects are more significant in the deformation in surface of materials [1]-[3], in which reduction of the surface roughness based on the increasing of plastic deformation of surface asperity was effective [4]. On the other hand, the effect on deformation behavior of the bulk region indicted reduction in the yield stress of materials, and not only acoustic effect [5], but also impact effect is found to generate a large amount of dislocation and produce plastic deformation [6][7]. However, the effect on the bulk is more significant as that on the surface. Differences in the effect on the surface and the bulk are not clarified. In this study, the mechanism of the deformation in the surface of the material with ultrasonic vibration assistance is investigated and compared with that in the bulk. Forging tests using a newly developed ultrasonic vibrator were carried out on pure Cu foils with various process conditions. The longitudinal vibration frequency of the ultrasonic transducer is 60∓2kHz, and the vibration amplitude is in an adjustable range of 0~10μm. Forging test was carried out at different initial stress, specimen size and amplitude. The difference in acoustic softening and impact effects on the surface and the bulk was discussed.

Supercapacitor electrodes based on modified titania nanotube arrays on flexible substrates

Highly ordered titania nanotube arrays were synthesised on titanium metal foil through electrochemical anodisation. The annealed samples were characterised through scanning electron microscopy and X-ray diffraction analysis. The electrochemical characterisations of the arrays were done through cyclic voltammetry, galvanostatic charge discharge and electrochemical impedance spectroscopy analyses. The titania nanotube arrays exhibited a specific capacitance of 6.8 mF cm–2 at 5 mV s–1 scan rate, which is very much higher than that reported earlier. Pseudocapacitive metal oxides were deposited on these arrays forming composite supercapacitor electrodes and their supercapacitor properties were compared with same deposited on bare titanium foil substrates. Pseudocapacitive metal oxides deposited on these titania nanotube array substrates exhibited improved supercapacitor performance and stability over the same deposited on titanium foil substrates.

Electrochemical Performance of Orthorhombic CsPbI3 Perovskite in Li-Ion Batteries

A facile solution process was employed to prepare CsPbI3 as an anode material for Li-ion batteries. Rietveld refinement of the X-ray data confirms the orthorhombic phase of CsPbI3 at room temperature. As obtained from bond valence calculations, strained bonds between Pb and I are identified within PbI6 octahedral units. Morphological study shows that the as-prepared δ-CsPbI3 forms a nanorod-like structure. The XPS analysis confirm the presence of Cs (3d, 4d), Pb (4d, 4f, 5d) and I (3p,3d, 4d). The lithiation process involves both intercalation and conversion reactions, as confirmed by cyclic voltammetry (CV) and first-principles calculations. Impedance spectroscopy coupled with the distribution function of relaxation times identifies charge transfer processes due to Li metal foil and anode/electrolyte interfaces. An initial discharge capacity of 151 mAhg−1 is found to continuously increase to reach a maximum of ~275 mAhg−1 at 65 cycles, while it drops to ~240 mAhg−1 at 75 cycles and then slowly decreases to 235 mAhg−1 at 100 cycles. Considering the performance and structural integrity during electrochemical performance, δ-CsPbI3 is a promising material for future Li-ion battery (LIB) application.

Research on MEMS multi-point exploding metal foil synchronous array

Based on MEMS technology, this paper realized the chip preparation of the synchronous initiation array and obtained the ideal process parameters. The MEMS multi-point exploding metal foil synchronous array chip replaces the traditional initiation array composed of electric detonators, and has a greatly reduced volume and could be prepared in batches. By testing the electrical explosion parameters of the array chip, the peak voltage, peak current, peak time and other data of different ignition voltages are obtained. At the same time, we proposed a method to test the synchronization of the array using multi-channel photonic doppler velocimetry, and obtained the synchronization data when the firing voltage was 2500 V and 2800 V, which provided help for the subsequent optimization design.

On the in-situ on-line structural health monitoring of composites using screen-printed sensors

This study aims at developing the screen-printed sensors as a viable means of depositing sensing tracks on composites for their on-line structural health monitoring. Conventional silk screen was employed in order to deposit a nano-composite solution comprising of a conductive nano-filler (carbon nano-particles) dispersed in a thermoplastic matrix (high density polystyrene) on laminated composite specimens. The solution was deposited using a squeegee and was allowed to dry. Commercially available metal foil strain gauges were also bonded alongside screen-printed sensor in order to compare the response of the screen-printed sensors with the commercially available strain gauges. The sensing ability of these screen-printed sensors was tested on a universal testing machine (MTS 810) in four-point bending configuration using a load cell of 100 kN. The sensor deposited using screen-printing technique underwent tensile loading at the lower side of the laminate. A data linearization and amplification module comprising of commercially available instrumentation amplifier (INA 118) was used in conjunction with data acquisition module (Keithley KUSB 3100). The results obtained show that the screen-printed sensors have higher gauge factors in tensile loading scenario with reasonably linear response as compared to traditional metal foil strain gauges. The ease of the deposition of a nano-composite solution via screen printing also makes the technique a viable alternative to the traditional resin bonded metal foil strain gauges which have to be bonded on the surface. Moreover, screen printing offers unlimited options for the development of smart composites in various configurations for a multitude of structural applications.